2.4- Dichlorobenzoic acids, oxidation

Furosemide can also be synthesized starting with 2,4-dichlorobenzoic acid (formed by chlorination and oxidation of toluene). Reaction with chlorosulfonic acid is an electrophilic aromatic substitution via the species -S02C1 attacking ortho and para to the chlorines and meta to the carboxy-late. Ammonolysis to the sulfonamide is followed by nucleophilic aromatic substitution of the less hindered chlorine by furfurylamine (obtained from furfural—a product obtained by the hydrolysis of carbohydrates). 

Numerous individual substances were detected only in Ru04 extracts e.g. di- to pentachlorinated benzenes, 4-chlorobenzoic acid and 2,4-dichlorobenzoic acid 24, hexachlorocyclohexanes (a-,P-,y- and 5-HCH) 22, a technical mixture obtained during the synthesis of lindane, and the plasticizers alkylsulfonic acid phenylesters 23. These plasticizers were recently identified in riverine sediments (Franke et al. 1998). Furthermore, nitro-substituted benzoic acid and alkylated phenols 24 were observed. The occurrence of aromatic nitro compounds as a result of the oxidation of anilines can be excluded due to the contemporary appearance of amino compounds, e.g. 4-aminobenzoic acid or N-ethylaniline. However, the origin as well as the emission pathway of these compounds is still unknown. 

Numerous other applications of ETA have been described (182,188.189). Compounds or materials studied by this technique include barium salts of phthalic. isophthalic, terephthalic, benzoic, salicylic, 1.4-aminobenzoic. 1,2-dichlorobenzoic and 1.2-diiodobenzoic acids (197) uranyl gels (198. 204) ferric oxide (199) cement (200, 201) powder metallurgy 1192) Ge0, 5Te0.6o Se0 i5 1202) anatase (TiOi), gibbsite, and kaolinite (193) thoria iThCK) powder (204) and many others. 

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